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<h1 id="sec_name">
<span data-if="hdevelop" style="display:inline;">fread_string</span><span data-if="c" style="display:none;">T_fread_string</span><span data-if="cpp" style="display:none;">FreadString</span><span data-if="dotnet" style="display:none;">FreadString</span><span data-if="python" style="display:none;">fread_string</span> (算子名称)</h1>
<h2>名称</h2>
<p><code><span data-if="hdevelop" style="display:inline;">fread_string</span><span data-if="c" style="display:none;">T_fread_string</span><span data-if="cpp" style="display:none;">FreadString</span><span data-if="dotnet" style="display:none;">FreadString</span><span data-if="python" style="display:none;">fread_string</span></code> — Read a string from a text file.</p>
<h2 id="sec_synopsis">参数签名</h2>
<div data-if="hdevelop" style="display:inline;">
<p>
<code><b>fread_string</b>( :  : <a href="#FileHandle"><i>FileHandle</i></a> : <a href="#OutString"><i>OutString</i></a>, <a href="#IsEOF"><i>IsEOF</i></a>)</code></p>
</div>
<div data-if="c" style="display:none;">
<p>
<code>Herror <b>T_fread_string</b>(const Htuple <a href="#FileHandle"><i>FileHandle</i></a>, Htuple* <a href="#OutString"><i>OutString</i></a>, Htuple* <a href="#IsEOF"><i>IsEOF</i></a>)</code></p>
</div>
<div data-if="cpp" style="display:none;">
<p>
<code>void <b>FreadString</b>(const HTuple&amp; <a href="#FileHandle"><i>FileHandle</i></a>, HTuple* <a href="#OutString"><i>OutString</i></a>, HTuple* <a href="#IsEOF"><i>IsEOF</i></a>)</code></p>
<p>
<code>HString <a href="HFile.html">HFile</a>::<b>FreadString</b>(Hlong* <a href="#IsEOF"><i>IsEOF</i></a>) const</code></p>
</div>
<div data-if="com" style="display:none;"></div>
<div data-if="dotnet" style="display:none;">
<p>
<code>static void <a href="HOperatorSet.html">HOperatorSet</a>.<b>FreadString</b>(<a href="HTuple.html">HTuple</a> <a href="#FileHandle"><i>fileHandle</i></a>, out <a href="HTuple.html">HTuple</a> <a href="#OutString"><i>outString</i></a>, out <a href="HTuple.html">HTuple</a> <a href="#IsEOF"><i>isEOF</i></a>)</code></p>
<p>
<code>string <a href="HFile.html">HFile</a>.<b>FreadString</b>(out int <a href="#IsEOF"><i>isEOF</i></a>)</code></p>
</div>
<div data-if="python" style="display:none;">
<p>
<code>def <b>fread_string</b>(<a href="#FileHandle"><i>file_handle</i></a>: HHandle) -&gt; Tuple[str, int]</code></p>
</div>
<h2 id="sec_description">描述</h2>
<p>该算子 <code><span data-if="hdevelop" style="display:inline">fread_string</span><span data-if="c" style="display:none">fread_string</span><span data-if="cpp" style="display:none">FreadString</span><span data-if="com" style="display:none">FreadString</span><span data-if="dotnet" style="display:none">FreadString</span><span data-if="python" style="display:none">fread_string</span></code> reads a string from the
input file defined by the handle <a href="#FileHandle"><i><code><span data-if="hdevelop" style="display:inline">FileHandle</span><span data-if="c" style="display:none">FileHandle</span><span data-if="cpp" style="display:none">FileHandle</span><span data-if="com" style="display:none">FileHandle</span><span data-if="dotnet" style="display:none">fileHandle</span><span data-if="python" style="display:none">file_handle</span></code></i></a>.
The input file must have been opened with <a href="open_file.html"><code><span data-if="hdevelop" style="display:inline">open_file</span><span data-if="c" style="display:none">open_file</span><span data-if="cpp" style="display:none">OpenFile</span><span data-if="com" style="display:none">OpenFile</span><span data-if="dotnet" style="display:none">OpenFile</span><span data-if="python" style="display:none">open_file</span></code></a> in text format.
</p>
<p>A string begins with the first character that is not a separator, i.e., that
is no white space or line break: all other characters, mainly letters,
numbers, and all other printable characters, but also all other control
characters that are no separators are added to the output string.
The string ends at the first separator character after one or more
accepted characters, or when the end of the file was reached.
The terminating separator character is not added to the output string, but
the file position indicator remains after it. Thus, a subsequent read
operation on the file would start after the terminating separator character.
The read character sequence is returned in parameter <a href="#OutString"><i><code><span data-if="hdevelop" style="display:inline">OutString</span><span data-if="c" style="display:none">OutString</span><span data-if="cpp" style="display:none">OutString</span><span data-if="com" style="display:none">OutString</span><span data-if="dotnet" style="display:none">outString</span><span data-if="python" style="display:none">out_string</span></code></i></a>.
If needed, the output string is transcoded into the current encoding of the
HALCON library (the default is UTF-8).
</p>
<p>The range of characters that are handled as separator depends on the
file encoding, which can be specified when the file is opened.
The character <i><span data-if="hdevelop" style="display:inline">' '</span><span data-if="c" style="display:none">" "</span><span data-if="cpp" style="display:none">" "</span><span data-if="com" style="display:none">" "</span><span data-if="dotnet" style="display:none">" "</span><span data-if="python" style="display:none">" "</span></i> (space) and the standard ASCII whitespace control
characters
<i><span data-if="hdevelop" style="display:inline">'\t'</span><span data-if="c" style="display:none">"\t"</span><span data-if="cpp" style="display:none">"\t"</span><span data-if="com" style="display:none">"\t"</span><span data-if="dotnet" style="display:none">"\t"</span><span data-if="python" style="display:none">"\t"</span></i> (tab),
<i><span data-if="hdevelop" style="display:inline">'\f'</span><span data-if="c" style="display:none">"\f"</span><span data-if="cpp" style="display:none">"\f"</span><span data-if="com" style="display:none">"\f"</span><span data-if="dotnet" style="display:none">"\f"</span><span data-if="python" style="display:none">"\f"</span></i> (form feed),
<i><span data-if="hdevelop" style="display:inline">'\n'</span><span data-if="c" style="display:none">"\n"</span><span data-if="cpp" style="display:none">"\n"</span><span data-if="com" style="display:none">"\n"</span><span data-if="dotnet" style="display:none">"\n"</span><span data-if="python" style="display:none">"\n"</span></i> (line feed),
<i><span data-if="hdevelop" style="display:inline">'\r'</span><span data-if="c" style="display:none">"\r"</span><span data-if="cpp" style="display:none">"\r"</span><span data-if="com" style="display:none">"\r"</span><span data-if="dotnet" style="display:none">"\r"</span><span data-if="python" style="display:none">"\r"</span></i> (carriage return), and
<i><span data-if="hdevelop" style="display:inline">'\v'</span><span data-if="c" style="display:none">"\v"</span><span data-if="cpp" style="display:none">"\v"</span><span data-if="com" style="display:none">"\v"</span><span data-if="dotnet" style="display:none">"\v"</span><span data-if="python" style="display:none">"\v"</span></i> (vertical tab)
are all accepted as separator on all locales or when the encoding has to be
ignored.
Other encodings may provide additional separator characters, e.g.,
Latin-1 defines <i><span data-if="hdevelop" style="display:inline">'0xA0'</span><span data-if="c" style="display:none">"0xA0"</span><span data-if="cpp" style="display:none">"0xA0"</span><span data-if="com" style="display:none">"0xA0"</span><span data-if="dotnet" style="display:none">"0xA0"</span><span data-if="python" style="display:none">"0xA0"</span></i> (no-break space) or Shift-JIS (as many other
Asian encodings) defines <i><span data-if="hdevelop" style="display:inline">'0x8140'</span><span data-if="c" style="display:none">"0x8140"</span><span data-if="cpp" style="display:none">"0x8140"</span><span data-if="com" style="display:none">"0x8140"</span><span data-if="dotnet" style="display:none">"0x8140"</span><span data-if="python" style="display:none">"0x8140"</span></i> (ideographic space) as valid
separator.
UTF-8 handles these characters also as a separator just as all other
code points which in the Unicode standard are defined as white spaces in
the categories space separators <em>Zs</em>, line separators <em>Zl</em>, and
paragraph separators <em>Zp</em>.
</p>
<p>If the end of the file is reached before any character was written to the
output string, <a href="#IsEOF"><i><code><span data-if="hdevelop" style="display:inline">IsEOF</span><span data-if="c" style="display:none">IsEOF</span><span data-if="cpp" style="display:none">IsEOF</span><span data-if="com" style="display:none">IsEOF</span><span data-if="dotnet" style="display:none">isEOF</span><span data-if="python" style="display:none">is_eof</span></code></i></a> 返回值 <i>1</i>, otherwise
<i>0</i>.
</p>
<p>该算子 <code><span data-if="hdevelop" style="display:inline">fread_string</span><span data-if="c" style="display:none">fread_string</span><span data-if="cpp" style="display:none">FreadString</span><span data-if="com" style="display:none">FreadString</span><span data-if="dotnet" style="display:none">FreadString</span><span data-if="python" style="display:none">fread_string</span></code> emits a low-level error message, when
it encounters bytes that do not represent a valid code point in the
specified encoding.
Despite of the low-level error message, 该算子 will not fail and
<a href="#OutString"><i><code><span data-if="hdevelop" style="display:inline">OutString</span><span data-if="c" style="display:none">OutString</span><span data-if="cpp" style="display:none">OutString</span><span data-if="com" style="display:none">OutString</span><span data-if="dotnet" style="display:none">outString</span><span data-if="python" style="display:none">out_string</span></code></i></a> will contain potentially invalid bytes
(invalid within the specified encoding).
Furthermore, 该算子 also emits a low-level error message, when the
output string cannot be transcoded without loss of information into the
current encoding of the HALCON library.
For a correctly encoded string this can only happen when the file is
UTF-8 encoded and the current encoding of the HALCON library is
<i><span data-if="hdevelop" style="display:inline">'locale'</span><span data-if="c" style="display:none">"locale"</span><span data-if="cpp" style="display:none">"locale"</span><span data-if="com" style="display:none">"locale"</span><span data-if="dotnet" style="display:none">"locale"</span><span data-if="python" style="display:none">"locale"</span></i> (see <a href="set_system.html"><code><span data-if="hdevelop" style="display:inline">set_system(::'filename_encoding','locale':)</span><span data-if="c" style="display:none">set_system("filename_encoding","locale")</span><span data-if="cpp" style="display:none">SetSystem("filename_encoding","locale")</span><span data-if="com" style="display:none">SetSystem("filename_encoding","locale")</span><span data-if="dotnet" style="display:none">SetSystem("filename_encoding","locale")</span><span data-if="python" style="display:none">set_system("filename_encoding","locale")</span></code></a>).
</p>
<h2 id="sec_execution">运行信息</h2>
<ul>
  <li>多线程类型:可重入(与非独占操作符并行运行)。</li>
<li>多线程作用域:全局(可以从任何线程调用)。</li>
  <li>未经并行化处理。</li>
</ul>
<h2 id="sec_parameters">参数表</h2>
  <div class="par">
<div class="parhead">
<span id="FileHandle" class="parname"><b><code><span data-if="hdevelop" style="display:inline">FileHandle</span><span data-if="c" style="display:none">FileHandle</span><span data-if="cpp" style="display:none">FileHandle</span><span data-if="com" style="display:none">FileHandle</span><span data-if="dotnet" style="display:none">fileHandle</span><span data-if="python" style="display:none">file_handle</span></code></b> (input_control)  </span><span>file <code>→</code> <span data-if="dotnet" style="display:none"><a href="HFile.html">HFile</a>, </span><span data-if="dotnet" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="python" style="display:none">HHandle</span><span data-if="cpp" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="c" style="display:none">Htuple</span><span data-if="hdevelop" style="display:inline"> (handle)</span><span data-if="dotnet" style="display:none"> (<i>IntPtr</i>)</span><span data-if="cpp" style="display:none"> (<i>HHandle</i>)</span><span data-if="c" style="display:none"> (<i>handle</i>)</span></span>
</div>
<p class="pardesc">File handle.</p>
</div>
  <div class="par">
<div class="parhead">
<span id="OutString" class="parname"><b><code><span data-if="hdevelop" style="display:inline">OutString</span><span data-if="c" style="display:none">OutString</span><span data-if="cpp" style="display:none">OutString</span><span data-if="com" style="display:none">OutString</span><span data-if="dotnet" style="display:none">outString</span><span data-if="python" style="display:none">out_string</span></code></b> (output_control)  </span><span>string <code>→</code> <span data-if="dotnet" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="python" style="display:none">str</span><span data-if="cpp" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="c" style="display:none">Htuple</span><span data-if="hdevelop" style="display:inline"> (string)</span><span data-if="dotnet" style="display:none"> (<i>string</i>)</span><span data-if="cpp" style="display:none"> (<i>HString</i>)</span><span data-if="c" style="display:none"> (<i>char*</i>)</span></span>
</div>
<p class="pardesc">Read character sequence.</p>
</div>
  <div class="par">
<div class="parhead">
<span id="IsEOF" class="parname"><b><code><span data-if="hdevelop" style="display:inline">IsEOF</span><span data-if="c" style="display:none">IsEOF</span><span data-if="cpp" style="display:none">IsEOF</span><span data-if="com" style="display:none">IsEOF</span><span data-if="dotnet" style="display:none">isEOF</span><span data-if="python" style="display:none">is_eof</span></code></b> (output_control)  </span><span>integer <code>→</code> <span data-if="dotnet" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="python" style="display:none">int</span><span data-if="cpp" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="c" style="display:none">Htuple</span><span data-if="hdevelop" style="display:inline"> (integer)</span><span data-if="dotnet" style="display:none"> (<i>int</i> / </span><span data-if="dotnet" style="display:none">long)</span><span data-if="cpp" style="display:none"> (<i>Hlong</i>)</span><span data-if="c" style="display:none"> (<i>Hlong</i>)</span></span>
</div>
<p class="pardesc">Reached end of file before any character was added to the
output string.</p>
</div>
<div data-if="hdevelop" style="display:inline">
<h2 id="sec_example_hdevelop">例程 (HDevelop)</h2>
<pre class="example">
fwrite_string(FileHandle,'Please enter text and return: ..')
fread_string(FileHandle,String,IsEOF)
fwrite_string(FileHandle,['here it is again: ',String])
fnew_line(FileHandle)
</pre>
</div>
<div data-if="c" style="display:none">
<h2 id="sec_example_c">例程 (C)</h2>
<pre class="example">
fwrite_string(FileHandle,"Please enter text and return: ..");
fread_string(FileHandle,&amp;String,&amp;IsEOF);
fwrite_string(FileHandle,"here it is again: ");
fwrite_string(FileHandle,String);
fnew_line(FileHandle);
</pre>
</div>
<div data-if="cpp" style="display:none">
<h2 id="sec_example_cpp">例程 (HDevelop)</h2>
<pre class="example">
fwrite_string(FileHandle,'Please enter text and return: ..')
fread_string(FileHandle,String,IsEOF)
fwrite_string(FileHandle,['here it is again: ',String])
fnew_line(FileHandle)
</pre>
</div>
<div data-if="com" style="display:none">
<h2 id="sec_example_com">例程 (HDevelop)</h2>
<pre class="example">
fwrite_string(FileHandle,'Please enter text and return: ..')
fread_string(FileHandle,String,IsEOF)
fwrite_string(FileHandle,['here it is again: ',String])
fnew_line(FileHandle)
</pre>
</div>
<div data-if="dotnet" style="display:none">
<h2 id="sec_example_dotnet">例程 (HDevelop)</h2>
<pre class="example">
fwrite_string(FileHandle,'Please enter text and return: ..')
fread_string(FileHandle,String,IsEOF)
fwrite_string(FileHandle,['here it is again: ',String])
fnew_line(FileHandle)
</pre>
</div>
<h2 id="sec_result">结果</h2>
<p>If a file is open and a suitable string is read, <code><span data-if="hdevelop" style="display:inline">fread_string</span><span data-if="c" style="display:none">fread_string</span><span data-if="cpp" style="display:none">FreadString</span><span data-if="com" style="display:none">FreadString</span><span data-if="dotnet" style="display:none">FreadString</span><span data-if="python" style="display:none">fread_string</span></code>
返回值 <TT>2</TT> (
      <TT>H_MSG_TRUE</TT>)
    .
Otherwise, an exception is raised.
Encoding errors have no influence on the result state.
</p>
<h2 id="sec_predecessors">可能的前置算子</h2>
<p>
<code><a href="open_file.html"><span data-if="hdevelop" style="display:inline">open_file</span><span data-if="c" style="display:none">open_file</span><span data-if="cpp" style="display:none">OpenFile</span><span data-if="com" style="display:none">OpenFile</span><span data-if="dotnet" style="display:none">OpenFile</span><span data-if="python" style="display:none">open_file</span></a></code>
</p>
<h2 id="sec_successors">可能的后置算子</h2>
<p>
<code><a href="close_file.html"><span data-if="hdevelop" style="display:inline">close_file</span><span data-if="c" style="display:none">close_file</span><span data-if="cpp" style="display:none">CloseFile</span><span data-if="com" style="display:none">CloseFile</span><span data-if="dotnet" style="display:none">CloseFile</span><span data-if="python" style="display:none">close_file</span></a></code>
</p>
<h2 id="sec_alternatives">可替代算子</h2>
<p>
<code><a href="fread_char.html"><span data-if="hdevelop" style="display:inline">fread_char</span><span data-if="c" style="display:none">fread_char</span><span data-if="cpp" style="display:none">FreadChar</span><span data-if="com" style="display:none">FreadChar</span><span data-if="dotnet" style="display:none">FreadChar</span><span data-if="python" style="display:none">fread_char</span></a></code>, 
<code><a href="read_string.html"><span data-if="hdevelop" style="display:inline">read_string</span><span data-if="c" style="display:none">read_string</span><span data-if="cpp" style="display:none">ReadString</span><span data-if="com" style="display:none">ReadString</span><span data-if="dotnet" style="display:none">ReadString</span><span data-if="python" style="display:none">read_string</span></a></code>, 
<code><a href="fread_line.html"><span data-if="hdevelop" style="display:inline">fread_line</span><span data-if="c" style="display:none">fread_line</span><span data-if="cpp" style="display:none">FreadLine</span><span data-if="com" style="display:none">FreadLine</span><span data-if="dotnet" style="display:none">FreadLine</span><span data-if="python" style="display:none">fread_line</span></a></code>
</p>
<h2 id="sec_see">参考其它</h2>
<p>
<code><a href="open_file.html"><span data-if="hdevelop" style="display:inline">open_file</span><span data-if="c" style="display:none">open_file</span><span data-if="cpp" style="display:none">OpenFile</span><span data-if="com" style="display:none">OpenFile</span><span data-if="dotnet" style="display:none">OpenFile</span><span data-if="python" style="display:none">open_file</span></a></code>, 
<code><a href="close_file.html"><span data-if="hdevelop" style="display:inline">close_file</span><span data-if="c" style="display:none">close_file</span><span data-if="cpp" style="display:none">CloseFile</span><span data-if="com" style="display:none">CloseFile</span><span data-if="dotnet" style="display:none">CloseFile</span><span data-if="python" style="display:none">close_file</span></a></code>, 
<code><a href="fread_char.html"><span data-if="hdevelop" style="display:inline">fread_char</span><span data-if="c" style="display:none">fread_char</span><span data-if="cpp" style="display:none">FreadChar</span><span data-if="com" style="display:none">FreadChar</span><span data-if="dotnet" style="display:none">FreadChar</span><span data-if="python" style="display:none">fread_char</span></a></code>, 
<code><a href="fread_line.html"><span data-if="hdevelop" style="display:inline">fread_line</span><span data-if="c" style="display:none">fread_line</span><span data-if="cpp" style="display:none">FreadLine</span><span data-if="com" style="display:none">FreadLine</span><span data-if="dotnet" style="display:none">FreadLine</span><span data-if="python" style="display:none">fread_line</span></a></code>
</p>
<h2 id="sec_module">模块</h2>
<p>
Foundation</p>
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